This just in from our anti-spam/-virus proxy,

System Status Notification: A spammer got the entire Amazon EC2 cloud black-listed on Spamhaus yesterday, despite Amazon's zero-tolerance spam policy, causing disruption to (some) email deliveries from our SMTP servers. We have applied for immediate and permanent de-listing, and meanwhile, D2S is queueing all RBL-blocked messages. To obtain immediate delivery, customers should suspend from any DNSBL checks performed by their domain's mail server, or explicitly white-list our IP addresses [,,] so they're exempted from RBL lookups.

Where is the global or RBL adjustments in ZCS server that needs to be made?